1. Field of the Invention
This invention relates to a vaccine for immunization against swine trichinosis. More particularly, this invention relates to a novel vaccine for swine trichinosis wherein the immunogenic substance is an antigen preparation of inert newborn larvae of Trichinella spiralis ("T. spiralis").
2. Description of the Prior Art
Current strategies for controlling T. spiralis, the causative agent of trichinosis in swine, include antemortem and postmortem inspection and meat processing including curing, freezing and cooking. Yet, T. spiralis continues to cause the pork industry more than four hundred million dollars per year. Consequently, there exists a need for a more effective approach to the control of this parasite.
One such approach recognized in the prior art is the development of a vaccine for immunization against T. spiralis. Research on the antigens of this parasite has been encouraged toward this effort. For example, stichosome antigens derived from the muscle larvae and extracts of adult stages has been reported to be moderately effective in inducing immunity. D. D. Despommier [Parasit. Immunol. 3: 261-272 (1982)]; H. R. Gamble [J. Parasit. 71: 680-682 (1985)]. Isolation and characterization of stichosome antigens by immunoaffinity purification with monoclonal antibodies has also been achieved. H. R. Gamble [Exp. Parasitol. 59: 398-404 (1985)]; D. S. Silberstein et al. [J. Parasit. 71: 516-517 (1985)]; D. S. Silberstein et al. [Science 227: 948-950 (1985)]. However, these antigens have only been moderately protective in swine immunization trials. K. D. Murrell et al. [Vet. Parasitol. 15: 263-270 (1984)]; H. R. Gamble et al. [Am. J. Vet. Res. 47: 2396-2399 (1986)].
It has also been shown that the surface of the newborn larvae of T. spiralis is antigenically diverse and stage specific, M. Philipp et al. [J. Exp. Med. 154: 210-215 (1981)]; M. Jungery et al. [Mol Biochem. Parasitol. 7: 101-109 (1983)], and that significant changes in the antigenic complexity of the newborn larvae surface occurs during its maturation. G. Ortega-Pierres et al. [Parasit. et al. Immunol. 6: 275-284 (1984)]. Further, antibodies to viable newborn larvae of T. spiralis have been shown to passively transfer protective immune response in rodents. D. D. Despommier [J. Parasitol. 57: 531-534 (1971)]. However, freeze-thaw killed newborn larvae were not effective in inducing aquired immunity in rodents. D. D. Despommier, Ibid.
The results of prior research does suggest the prospect of producing a vaccine against T. spiralis. However, until now there has been no vaccine which induces a significant level of immune response against T. spiralis in swine.
SUMMARY OF THE INVENTION
We have now developed a vaccine which unexpectedly produces greater than 60% protective immunity in swine against T. spiralis. The vaccine comprises inert newborn larvae of T. spiralis emulsified with a suitable adjuvant. The vaccine provides a method for immunizing swine against T. spiralis by inoculating the animal with an effective immunizing amount of the invention vaccine.
Accordingly, it is an object of this invention to provide a vaccine for swine trichinosis which produces a high level of protective immunity in swine.
Another object of this invention is to provide a method of immunizing swine against trichinosis through vaccination.